The overarching goal of this research program is to develop efficient systems to heterologously express natural product biosynthetic genes and pathways. Hence, this program will develop underlying technology required for "universal expression systems", especially as applied to marine cyanobacterial natural products. Further, the underlying technology to be developed for this purpose, "chemical complementation", is ideally suited to the rapid isolation of the genes encoding for natural products biosynthesis. This represents fundamental technology that will enhance the success of combinatorial biosynthesis as a method for producing libraries of natural product-like structures. Hence, this application addresses three of the focus areas defined in the RFA. The efforts described in this application represent the fusion of two research groups, creating a novel interface between natural products chemistry and innovative genetic selection systems and gene manipulations. The specific aims of this project are: 1) to engineer strains of Saccharomyces cerevisiae and Escherichia coli to recognize and grow only in the presence of the exogenously supplied marine cyanobacterial natural product lyngbyatoxin A; 2) to functionally express the lyngbyatoxin prenyl transferase in the above two engineered systems as a 'proof of the concept' of merging secondary metabolite biosynthesis with chemical complementation; 3) to use the above engineered strains to accomplish whole pathway functional gene expression with the lyngbyatoxin model, and to systematically modify these strains so as to overcome quantitative limitations on their expression; 4) to use the chemical complementation approaches developed above to rapidly express the biosynthetic gene clusters for several other marine cyanobacterial natural products available in our laboratories, thus demonstrating the generality of the method; 5) to compare the above chemical complementation strategy above with a genetic and chemical screening approach of a cyanobacterial fosmid library in genetically modified E. coli strains.